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(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD. No 592,357. Patented Oct. 26,1897.

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llNiTnp STATES PATENT Trice.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGGSlVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

lVl ULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,357, dated October26, 1897.

Application filed Jannaryt), 1890. Serial No. 386,379. (No model.)

To aZZ whom it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cookand State of Illinois, temporarily residing at Stuttgart, in the Empireof Germany, have invented certain new and useful Improvements inMultiple Switchboards for TelephoneEXchanges, of which the followingisafull, clear, concise, and exact description, reference being had tothe accompanying drawing, forming a part of this specification.

My invention relates to a single-circuit telephone-exchange system inwhich there is a cord and a plug attached to the cord for each linetowhich the line is normally connected. Said plug rests normally in aswitching device, and when it is desired to switch the line with anotherline for conversation the plug is taken from its normal position andplaced in the switch of the line wanted. Such a system is called asingle-cordsystem.

My invention consists of apparatus,circuits, and connections for eachline whereby the operator maycxpeditiously and with few operationsconnect her telephone to the circuit of the line when its call isindicated, may test the line wanted to see whether it is in use, mayconnect the two lines together, may send signaling-current over thelines, may receive a clearing-out signal, may connect her telephone intothe circuit to determine whether the subscribers are throughconversation, and may disconnect the lines and place the line apparatusin readiness for receiving a new call.

In the accompanying drawing, illustrating my invention, A and Arepresent sections of two multiple switchboards at the central office ofthe exchange to which the same lines connect. On each board is aspring-jack or similar switch for each line. Each switch has acontactspring which is normally in contact with a contact-point, but isseparated and insulated from the point while aplug is inserted intoit,'and a contact-piece which is normally insulated from the spring andis con nected with it while the plug is inserted into the switch. tohave a test-plug applied to it for testing. The springjacks shown in thedrawing are old.

This contact-piece is adapted- For each line is a switch by aid of whichthe operators telephone and calling-generator may be connected anddisconnected from the circuit of the line. As this switch is manipulatedby the operator in answering the calls of the line, I call it theansweringswitch of the line. Each line has also a switching device intowhich the switch-plug is placed normally or when it is not in use forswitching. This device grounds the circuit of the line when the plug isinserted into it and has contacts which perform other functions in theoperation of the system as the plug is in or out of the device and whichI shall hereinafter describe. I will designate this device as theplug-switching device of the line.

Two lines and their switches on the boards, their plugs and cords, theiransweringswitches, their annunciators, and their plugswitching devicesare shown in the drawing.

The drawing represents the answering apparatus of one of the lines aslocated at one of the boards and that of the other line as located atthe other board.

13 B represent the two answering-switches, C O the two plug-switchingdevices, and D D the two switch-plugs of the lines to which the flexiblecords are attached and which are adapted to be placed in any springjackswitch at the boardwhere they may be located; These switch-plugs haveeach a metal tip adapted to be inserted into any line'switch and wheninserted to press the spring of the switch from its contact-point andform connection with the spring, and they have also at the bottom oftheir handles metal sleeves in electrical connection with their tips.One plug is shown in its switching device and one plug is shown out ofits device ready to be inserted into the switch of any line. In theanswering-switches g g are rubberframes which support and insulate theparts.

ff are contact-springs.

1 and 2 are contact-points, of which 1 is mounted in close proximity tospring f and 2 in close proximity to f, so as to be brought into contactwith them, respectively, as will hereinafter be described.

d is a rod which slides through a hole in the end of the frame.

0 is a knob by which the operator slides the 7 rod in and out asrequired in order to make the required connections.

e 0 p is an irregularly-shaped metal contact-piece attached to the rodand which moves in and out between springs f f and is pressed upon bysaid springs as the rod is moved in and out by the operator. The knoband the metal piece afford stops which limit the inward and outwardmotions of the rod and the metal piece which it carries. As the rod andthe irregularly-shaped metal piece move as one piece and their functionis to change the circuit connections, I designate them as thecommutator-piece of the switch. The metal parts are insulated, as shown.The outer portion of the irregularlyshaped metal piece on which thecontactsprings are shown as hearing I have marked and designated aspiece 6. The center portion is marked 0 and the inner portion of thepiece is marked 19.

The surface of the com mutator-piece against which spring f presses hasa plane surface along 0 which extends far enough from the axis of thecommutator-piece in its line of motion that when the spring rests on 0it is pressed into contact with point 1. The surface of thecommutator-piece against which spring f presses has a plane surfacealong c which extends far enough from such axis of the commutator-piecethat when the spring rests one it is pressed into contact with point 2.In all other positions of the commutatorpiece the springs are not incontact with the points. In whatever position the commutator-piece maybe placed the springs f f bear on the metal piece 6 op, which thereforeelectrically connects orbridges them. When the springs rest on thecenter portion 0, spring f is in contact with piece 1 and spring f isout of contact with piece 2. When the springs rest on theinnerportionp,the springs ff are not in contact with either piece 1 or 2.

In the plug-switching devices 0 O, h is a metal contact-piece connectedto the ground with which the metal sleeve connected with the tip of theplug is in contact when the plug is in the device.

3, 45, 5-, and 6 are contact-pieces which are insulated from h and areinsulated from each other-when the plug is in the device. 4 and 6 arespring-contacts and the others may be without elasticity. They aremounted parallelto each other and in close juxtaposition. 4 is connectedwith 6 near its tip by an insulation-piece, so that it moves back andforth as 6 moves. Spring 6 has an insulation-piece 6, as shown, on theside where the switchplug presses when placed in the switching device.Piece 6 is an irregularly-shaped spring which bears on the plug when theplugis inserted, is insulated from the contact-piece of the plug, and ismoved by the plug on its insertion, so as to make the switch connectionsI shall now describe. l/Vhen the plug is in the device, it presses orwedges spring 6 away contact-piece 3 of the switching device.

; the lines together.

from contact with point 5,and spring 6 carries spring 4 away fromcontact with point 3. When the plug is withdrawn,the spring moves untilit comes in contact with piece 5 and it carries or forces piece 4 intocontact with piece 3.

k is a three-point key with the points arranged substantially as shown.

t is the operators telephone. B is her calling-generator. B is atest-battery, and T is 5 her test-plug, connected, as shown, through aflexible conductor.

shown: Each line passes successively through its pairs of switchcontact-points on the severalboards, passing in each case to the springfirst. It then passes through its annunciator to spring f of itsanswering'switch. The plug of the line is normally in its switchingdevice which then grounds its contact piece or sleeve through theconnection then established between it and piece h of the switchingdevice. This contact-sleeve is connected through a flexible conductor tospring f and is also connected with the metal tip of the plug. All thenormally-insulated contact-pieces of the lineswitches on the severalboards are connected together and are connected to contact-piece 5 ofthe plug-switching device. Contact-piece 6 of the switching device isconnected to the circuit of the cord conductor. Contact-piece 2 of theanswering-switch is connected with Oontact-piece 4 is connected throughthe operators telephone to the ground. Contact-piece 1 is connected withthe lever of the key, and the upper contact-point of the key isconnected through the calling-generator to the ground. The lowercontact-point of the key is connected to the telephone with thetelephone between said connection and the ground connection. Thetest-plug is connected through the telephone and test-battery to theground.

Each operator has but one telephone, one

1 calling-generator, one key, one test-battery and one test-plug. Theirconnection with the apparatus of the other lines assigned to her 1 toanswer will be readily understood.

The operation of the system is as follows:

i When an operator receives a call on a line, ;she removes the line-plugfrom its normal position.- By so doing she connects her tele- 1 phone,grounded at one end, to the circuit of the line. of contact-points 3 and4, the point 2 being also in connection with spring f, which is con- Theconnection is through the pair nected to the linev and completing theconnection. She then finds out what line is wanted and if on testing theline she finds that it is not in use she places the switchplug in theline-switch and thereby connects She then pulls the commutator-piece outas far as it will come and in so doing has disconnected her telephone 1from the line-circuit, has connected her calling-generator to thecircuit and rung the two bells, has disconnected the generator from thecircuit, and leaves the lines connected together for conversation. lVhenby this operation the spring f passes from piece 2, the connection withpiece 2 is broken and the telephone is disconnected from the circuit.-While the spring f remains on the piece 0, it is in contact with thepiece 1, and the calling-generator (the key not being depressed) isconnected, grounded on one side, to the circuit of the lines on itsother side. \Vhile the springs ff rest on the piece 1), the circni t ofthe lines is disconnected from both the operators telephone andgenerator and they are in a closed circuit for conversation with theannunciator of the line in which the call originated in their circuit.When the plug of a line is withdrawn from its normal position for use,the normally open test-circuit of the line is connected with the line,the connection being made through the pairs of contactpoints 5 and 6 ofthe switching device. .Vhen the plug is placed into the switch of theline wanted, the test'circuit of that line is also connected to thecircuit through the contact piece or sleeve of the plug. WVhen the plugis withdrawn and inserted into its normal position, both test-circuitsare again opened.

The test of the line is as follows: Its normally open testwire iscrossed or connected with it when it is switched for conversation eitherby its plug being taken from its normal position or the plug of anotherline being placed in one of its switches, and the test wire is thereforeconnected with the ground through the ground connection at thesubscribers station. lVhen the test-plug is connected to the test-pieceof a line and the line is not connected for use, no test-circuit iscompleted and the instrument will not sound. lVhen, however, the line isswitched for use, there is a complete circuit from the ground throughthe test receiving instrument and battery to the normally opentest-circuit of the line and thence to the line and to its ground at thesubscribers station and the instrument will sound or respond, indicatingthat the line is in use.

)Vhen an operator desires to find out by listening whether thesubscribers who are conneeted together are through conversation, shepresses down the lever of the key 7t" and while the lever is in thisposition pushes the commutator into its central position, and hertelephone, grounded on one side, is connected on its other side to thecircuit. Then this is done, the circuit of the two subscribers is notinterrupted, the telephone merely being conneeted as a third leg to thecircuit, the connection being from spring f to point 1 and thence to thekey 7s and its lower contact-point to ground through the telephone. Whenshe determines the condition of the line, she moves the commutator fromsuch position and then releases the key.

When she desires to clear out a connection,

she removes the plug from the switch and places it in its switchingdevice. She then while the key 7.; is depressed pushes thecommutator-piece into its inward position, (which is the position shownin the drawing.) lVhen the apparatus is in this condition, it is readyto receive a new order from the subscriber with no other motion of theoperator than to remove the plug from its normal position.

By the operation of the key It as described the operator can readilyconnect her telephone by a third leg to any circuit for listening andshe can also change the commutatonpiece from its outer position (whichis the one in which it remains while the subscribers are inconversation) to its inner position, where it is ready to receive callswithout sending a signalingcurrent over the line-circuit, as would bethe case were the signaling-generator not thereby disconnected from thecontactpiece 1 while the commutator-piece is passing its centralposition, where the spring f bears on the piece 1. I prefer to have thekey 7t actuated by a cam-lcver, as shown in the drawing, or to have someother mechanism by which the contact-spring of the key maybe placed inone or the other of its two positions and left there without thecontinued manipulation of the operator. 3y this means an operator mayplace the key in position where her telephone is connected to the leverand, leaving it there, be free to operate one after another of heransweringswitches, so as to listen on the circuits or to put them intheir normal condition.

The employment of the tWo pairs of contacts, that between f and 2 andthat between 3 and i and the circuit, as described, enables me toconnect a line to the operators telephone for receiving an order by themore act of withdrawing the plug from its normal position and then todisconnect the telephone from the circuit by the mere act of pulling thecommutator-piece to the position in which it remains while conversationis going on between the two subscribers.

The arrangement of the spring f, the contact-piece 1, normally connectedto the calling-generator, and the portion 0 of the commutator-pieceenables an operator to send a signal-current over the circuit of thelines connected by the mere act of withdrawing the commutator-piece fromits normal position to the one it occupies while conversation is go ingon.

It will be seen from the description of the operation of thecommutator-piece and the contacts with their connections operated uponby the commutator-piece that when the commutator-piece is in oneposition the operators telephone is connected with the line, that whenit is moved to another position the telephone is disconnected from theline and the generator is connected with the line, and that when it ismoved to another position both the telephone and generator aredisconnected from the line. It will also be seen that the option of thecommutator-piece of the line disconnect the telephone from the line,then connect the generator to the line, and finally leave the linedisconnected from either telephone or generator. This arrangement ofparts in connection with the key it and the connections to it, asdescribed, enable the operator to listen and to place the apparatus inits normal position for receiving orders without disturbance of thesubscribers.

By the organization as described the operator is enabled in a multiplesystem to answer a subscriber, make his connection, and call the linewanted with a minimum of operations and work. These operations aremerely to take his plug from its normal position, place 'her test-plugon the test-bolt of the line wanted, place the plug in the switch of theline wanted, and withdraw the commutator-piece into its outer position.

I claim as my invention and desire to secure by Letters Patent" 1. In atelephone exchange system, a switching device for a switch-plug normallyconnected to a line and in which the plug normally rests, said switchingdevice having two contact-points which are normally separated when theplug is in the device and are in contact while the plug is out of thedevice, and an answering-switch for the line having a pair ofcontact-points normally closed but open while the switch-commutator isdrawn from its normal position, and a pair of contact-points normallyopen but closed while the commutator is drawn from its normal positionand again open while the commutator rests in the position it occupieswhile its line is switched for conversation, said pair of contact-pointsof the switching device and said first-mentioned pair of contact-pointsof the answering-switch being in a circuit which connects the line tothe ground through the operators telephone, and the other pair ofcontact-points of the answering-switch being in a circuit which connectsthe switch-plug to the ground through theoperators callinggenerator,substantially as set forth.

2. In a telephone exchange system, an answering-switch for atelephone-line, having a pair of contact-points to one of which the lineis connected and to the other of which the operators telephone isconnected, grounded at its other end, and having another pair ofcontact-points to one of which the cord and plug of the line isconnected, and to the other of which the calling-generator is connected,grounded at its other end, in combination with a commutator-piececontaining a metal contact-piece on which rest said first-mentionedcontact-pieces of each pair and which electrically bridges or connectsthem, said commutator-piece being adapted to occupy three positions atthe will of the operator, in the first of which said first-mentionedpair of contact-points alone are in contact, in the second of which saidsecond pair of contactpoints alone are in contact, and in the third ofwhich neither of the two pairs are in contact, substantially as setforth.

3. In an answering-switch fora telephoneline, a contact-sprin g and'acontact-point on one side of said spring, in combination with a commutator-piece, adapted to be placed in three positions at the will ofthe operator and to press against said spring on its other side, saidcommutator-piece having three surfaces against which said springalternately presses, the middle surface being farthest from the centerof said commutator-piece in its line of motion,whereby when the springrests on said middle surface, and only then, it is in contact with saidcontact-point, substantially as set forth.

4. In an answering-switch for a telephoneline, a contact-spring and itscontact-point and another contact-spring and its contactpoint, incombination with a com mutator-piece adapted to be placed in threepositions and on which said springs press, said commutator-piece havingthree commutator-surfaces against which one of said springs alternatelypresses, the middle surface being farthest from the center of saidcommutator-piece in its line of motion,and having two othercommutator-surfacesagainst which the other spring alternately presses,the commu tator-surface on which said spring presses in the firstposition of the commutatonpiece being farther from the center of thecommutator-piece in its line of motion than the surface against whichthe spring presses in the two other positions of the commutator-piece,whereby in themiddle position of the commutator-piece, and only then,the first-mentioned spring is in contact with the first-mentioned point,and in the first position of the commutator-piece, and only then, thesecond-mentioned spring is in contact with the second-mentioned point,substantially as set forth.

5. In an answering-switch for a telephoneline, a contact-spring and itscontact-point and another contact-spring and its contactpoint, incombination with a commutatorpiece adapted to be placed in threepositions and on which said springs press, said commutator-piece havinga contact-piece of metal with three commutator-surfaces which one ofsaid springs alternately presses, the middle surface being farthest fromthe center of said commutator-piece in its line of motion, and two othercommutator-surfaces against against which the other spring alternatelypresses, the commutater-surfaces on which said spring presses in thefirst position of the connnutatonpiece being farther from the center ofthe commutator-piece in its line of motion than the surface againstwhich the spring presses in the two other positions of thecommutator-piece, whereby said springs are electrically connected, andin the middle position of the commutator-piece, and only then, thefirst-mentioned spring is in contact with the first-mentioned point, andin the first position of the commutatonpiece, and only then, thesecond-mentioned spring is in contact with the second-mentioned point,substantially as set forth.

6. In a telephone-exchange system, an operators switch having acontact-sprin g, a contact-point on one side of the spring and acommutatonpiece adapted to be placed in three positions at the will ofthe operator, and to press against said spring on its other side, saidcommutator-piece having three surfaces against which said springalternately presses, the middle surface being farthest from the centerof said commutator-piece in its line of motion, whereby when the springrests on said middle surface, and only then, it is in contact with saidcontact-point, in combination with a telephone-circuit connected to saidspring, a calling-generator and a circuit connection from said pointthrough said generator to ground, substantially as set forth.

7. In atelephoneexchange system, an operators switch having acontact-spring, a contact-point on one side of the spring and acommutator-piece adapted to be placed in three positions at the will ofthe operator, and to press against said spring 011 its other side, saidcommutator-piece having three surfaces against which said springalternately presses, the middle surface being farthest from the centerof said commutator-piece in its line of motion, whereby when the springrests on said middle surface, and only then, it is in contact with saidcontact-point, in combination with a telephone-circuit connected to saidspring, a calling-generator, a circuit connection from said pointpassing normally through said generator to ground, an operatorstelephone and a switch by which the operator may at will switch thegenerator out of and the telephone into said circuit connection,substantially as set forth.

8. In a telephone-exchange system, telephonelines and switch-plugs, onefor each line, each plug being adapted to be placed in a switch ofeither of the other lines and thereby connect its line with the otherline, in combination with an operators telephone grounded on one side, acallinggenerator grounded on one side,and a commutator-piece for eachline adapted to be moved in one plane or direction to occupy threeswitching positions in said plane, in. one of which the other side ofthe telephone is connected to the line, in another of which said side ofthe telephone is disconnected from the line and the other side of thecalling-generator is connected to the line, and in another of whichneither said other side of the telephone nor said other side of thegenerator is connected to the line.

9. In a telephone-exchange systenntwo telephone-lines temporarilyconnected together for conversation, in combination with an op eratorstelephone grounded on one side, a calling-generator grounded on oneside, and a commutator-piece adapted to be moved in one plane ordirection to occupy three switching positions in said plane, in one ofwhich the other side of the telephone is thereby connected to the line,in another of which said side of the telephone is thereby disconnectedfrom the line and the other side of the calling-generator is therebyconnected to the line, and in another of which neither said other sideof the telephone nor said other side of the generator is connected tothe line.

10. In a telephone-exchange system, tele phone-lines and switch-plugs,one for each line, each plug being adapted to be placed in a switch ofeither of the other lines and thereby connectits line with the otherline, in combination with an operators telephone, a calling-generatorgrounded on one side, and a commutator-piece for each line adapted to bemoved in one plane or direction to occupy three switching positions insaid plane, in one of which the telephone is connected to the line, inanother of which the telephone is disconnected from the line and theother side of the calling-generator is connected to the line, and inanother of which neither the telephone nor said other side of thegenerator is connected to the line.

In witness whereof I hereunto subscribe my name this 20th day ofDecember, 1889.

MILO G. KELLOGG. lVitnesses:

EMIL ABENHEIM, MAnoAnn'rIm Rtuun

